Carbonylation catalyst system

ABSTRACT

A catalyst system, which comprises: 
     a) a source of a Group VIII metal; 
     b) a phosphine having an aromatic substituent which contains an imino nitrogen atom; 
     c) a source of protons; and 
     d) a tertiary amine.

FIELD OF THE INVENTION

The present invention relates to a novel catalyst system comprising atertiary amine and to its use in the carbonylation of acetylenically andolefinically unsaturated compounds.

BACKGROUND OF THE INVENTION

Many processes are known in the art for the carbonylation ofacetylenically and olefinically unsaturated compounds. A review of suchprocesses is provided by J. Falbe, "New Syntheses with Carbon Monoxide",Springer-Verlag, Berlin Heidelberg New York, 1980. Typically, theprocesses involve the reaction of an acetylenically or olefinicallyunsaturated compound with carbon monoxide and, in some cases, anucleophilic compound having a removable hydrogen atom, in the presenceof a carbonylation catalyst system. In many instances, the carbonylationcatalyst system comprises a source of a Group VIII metal and a ligandsuch as a phosphine.

Recently, several processes for the carbonylation of acetylenically andolefinically unsaturated compounds have been disclosed which involve theuse of a carbonylation catalyst system comprising a Group VIII metalcompound, in particular a palladium compound, a phosphine and a protonicacid. The processes proceed with a remarkably high reaction rate.

European Patent Nos. EP-A1-106379. EP-A1-235864. EP-A1-274795 andEP-A1-279477 disclose processes for the carbonylation of olefinicallyunsaturated compounds in which a catalyst system comprising a palladiumcompound, a triarylphosphine and a protonic acid is used. In all of theexamples, the triarylphosphine used is a triphenylphosphine.

European Patent No. EP-A1-0186228 discloses a process for thecarbonylation of acetylenically unsaturated compounds in which acatalyst system comprising a palladium compound, a phosphine and aprotonic acid is used. The examples illustrate the use of optionallysubstituted hydrocarbyl phosphines such as triphenylphosphine.

More recently, several processes for the carbonylation of acetylenicallyand olefinically unsaturated compounds have been disclosed which involvethe use of a catalyst system comprising a palladium compound, apyridylphosphine and an acid.

European Patent Nos. EP-A1-259914, EP-A1-282142 and EP-A1-305012disclose processes for the carbonylation of olefinically unsaturatedcompounds in which a catalyst system comprising a palladium compound, apyridylphosphine and a protonic acid is used.

European Patent No. EP-A1-0271144 discloses a process for thecarbonylation of an acetylenically unsaturated compound in which acatalyst system comprising a palladium compound a pyridylphosphine and aprotonic acid is used.

None of the aforementioned European patent specifications disclosecatalyst systems which additionally comprise a tertiary amine, nor dothey suggest that such catalyst systems would be of interest in thecarbonylation of acetylenically and olefinically unsaturated compounds.Tertiary amines are basic compounds and so might be expected to have amarked inhibitory effect upon the performance of the acid-containingcatalyst system. Indeed, the Applicants have found that the performanceof triarylphosphine-based catalyst systems is markedly impaired in thecarbonylation of olefins when a tertiary amine is included.

It, however, has now been found that acetylenically and olefinicallyunsaturated compounds can be carbonylated at a good reaction rate usinga catalyst system comprising a palladium compound, a pyridylphosphine, aprotonic acid and a tertiary amine.

SUMMARY OF THE INVENTION

The present invention therefore provides a catalyst system whichcomprises:

a) a source of a Group VIII metal;

b) a phosphine having an aromatic substituent which contains an iminonitrogen atom;

c) a protonic acid; and

d) a tertiary amine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Catalyst systems according to the invention have been found to be highlyactive in the carbonylation of acetylenically and olefinicallyunsaturated compounds. This finding is very surprising and istechnically important because it means that acetylenically andolefinically unsaturated compounds can be carbonylated using the highlyactive Group VIII metals/pyridylphosphine/protonic acid catalyst systemsunder basic conditions. Many reactions which can only be satisfactorilyperformed under basic conditions are now possible. For example, it hasbeen found that esters of acid-sensitive hydroxy compounds such assilanols and tertiary alcohols may be prepared in good selectivity usingcatalyst systems according to the invention.

It has also been found that catalyst systems according to the inventionexhibit improved tolerance of allenes, which are common impurities ofacetylenically unsaturated compounds.

Still further, it has been found that alkoxymethoxyalkanoates may beprepared by carbonylating alkenes with alkanols and formaldehyde in thepresence of a catalyst system according to the invention.

Yet further it has been found that catalyst systems according to theinvention have prolonged stability compared with corresponding systemswhich lack a tertiary amine.

The catalyst system according to the invention comprises a source of aGroup VIII metal. The source of a Group VIII metal may be the metallicelement or, preferably, a Group VIII metal compound.

Examples of Group VIII metals are iron cobalt, nickel, ruthenium,rhodium, palladium, iridium and platinum.

The catalyst system according to the invention preferably comprises asource of a palladium compound.

Examples of compounds of Group VIII metals include salts, for example,salts of nitric acid; sulfuric acid; sulfonic acids; phosphonic acids;perhalic acids; carboxylic acids such as alkane carboxylic acids havingnot more than 12 carbon atoms, e.g. acetic acid; and hydrohalic acids.Since halide ions can be corrosive, salts of hydrohalic acids are notpreferred. Other examples of compounds of Group VIII metals includecomplexes, such as complexes with acetylacetonate, phosphines and/orcarbon monoxide. For example the compound of a Group VIII metal may bepalladium acetylacetonate, tetrakis-triphenylphosphinepalladium,bis-tri-o-tolylphosphinepalladium acetate,bis-diphenyl-2-pyridylphosphinepalladium acetate,tetrakis-diphenyl-2-pyridylphosphinepalladium,bis-di-o-tolylpyridylphosphinepalladium acetate, orbis-diphenylpyridylphosphinepalladium sulphate.

The catalyst system used in the process according to the inventionfurther comprises a phosphine having an aromatic substituent whichcontains an imino nitrogen atom.

As used herein, the term "imino nitrogen atom" means a nitrogen atomwhich may be represented in the structural formula of the aromaticsubstituent containing it by the formula ##STR1## For example, if thearomatic substituent is a pyridyl group, the structural formula of thearomatic substituent is ##STR2##

The phosphine preferably comprises one or two phosphorus atoms. Eachphosphorus atom has three substituents. At least one of thesesubstituents is an aromatic substituent which contains an imino nitrogenatom. The remaining substituents are preferably selected from optionallysubstituted aliphatic and aromatic hydrocarbyl groups. When thephosphine comprises more than one phosphorus atom, it is possible forone substituent to be shared by more than one phosphorus atom, as forexample in ##STR3##

The aromatic substituent which contains an imino nitrogen is preferablya 6-membered ring containing one, two or three nitrogen atoms. Thearomatic substituent may itself be optionally substituted.

When a substituent is said to be "optionally substituted" in thisspecification, unless otherwise stated, the substituent may beunsubstituted or substituted by one or more substituents. Examples ofsuitable substituents include halogen atoms; alkyl groups; alkoxygroups; haloalkyl groups; haloalkoxy groups; acyl groups; acyloxygroups; amino groups, preferably alkyl or dialkylamino groups; hydroxygroups; nitrile groups; arylamino groups; and aromatic hydrocarbylgroups.

An aliphatic hydrocarbyl group is preferably an alkyl group, for examplea C₁₋₄ alkyl group; or a cycloalkyl group, for example a C₃₋₆ cycloalkylgroup.

An aromatic hydrocarbyl group is preferably a phenyl group.

A halogen atom, as such or in a haloalkyl group, is preferably afluorine, chlorine or bromine atom.

An acyl group in an acyl, acyloxy or acylamino group is preferably aC₂₋₅ alkanoyl group such as acetyl.

Examples of aromatic substituents containing an imino nitrogen atom arepyridyl, pyrazinyl, quinolyl, isoquinolyl, pyrimidinyl, pyridazinyl,cinnolinyl, triazinyl, quinoxalinyl, and quinazolinyl. Preferredsubstituents are pyridyl and pyrimidyl.

An imino group in an aromatic substituent containing an imino nitrogenatom is preferably connected to a phosphorus atom through a singlebridging carbon atom. For example, if the aromatic substituent is apyridyl group, it is preferably connected through the carbon atom at the2-position in the pyridyl group. Accordingly, examples of preferredaromatic substituents containing an imino nitrogen atom are 2-pyridyl;2-pyrazinyl; 2-quinolyl; 1-isoquinolyl; 3-isoquinolyl; 2-pyrimidinyl;3-pyridazinyl; 3-cinnolinyl; 2-triazinyl; 2-quinoxalinyl; and2-quinazolinyl; 2-Pyridyl, 2-pyrimidyl and 2-triazinyl are particularlypreferred.

When the phosphine contains one phosphorus atom, it may conveniently berepresented by the general formula ##STR4## in which R¹ represents anaromatic substituent containing an imino nitrogen atom, and R² and R³,which may be the same or different, represent a group R¹ or anoptionally substituted aliphatic or aromatic hydrocarbyl group.

Particularly preferred phosphines are:

bisphenyl-(2-pyridyl)phosphine,

bis(2-pyridyl)phenylphosphine,

tris(2-pyridyl)phosphine,

diphenyl(6-methoxy-2-pyridyl)phosphine,

bis(6-ethoxy-2-pyridyl)phenylphosphine,

bis(6-chloro-2-pyridyl)phenylphosphine,

bis(6-bromo-2-pyridyl)phenylphosphine,

tris(6-methyl-2-pyridyl)phosphine,

bis(6-methyl-2-pyridyl)phenylphosphine,

bisphenyl(6-methyl-2-pyridyl)phosphine,

bis(3-methyl-2-pyridyl)phenylphosphine,

bisphenyl(4,6-dimethyl-2-pyridyl)phosphine,

di(n-butyl)-2-pyridylphosphine,

dimethyl-2-pyridylphosphine,

methyl phenyl-2-pyridylphosphine,

n-butyl tert-butyl 2-pyridylphosphine,

n-butyl(4-methoxyphenyl)(2-pyridyl)phosphine, and

methyl di(2-pyridyl)phosphine.

The catalyst system used in the process according to the inventionfurther comprises a protonic acid. The function of the protonic acid isto provide a source of protons. Accordingly, the protonic acid may begenerated in situ.

Preferably, the protonic acid is selected from acids having anon-coordinating anion. Examples of such acids include sulfuric acid; asulfonic acid, e.g. an optionally substituted hydrocarbylsulfonic acidsuch as benzenesulfonic acid, p-toluenesulfonic acid,naphthalenesulfonic acid; an alkylsulfonic acid such as methanesulfonicacid or tert-butylsulfonic acid, or 2-hydroxypropanesulfonic acid,trifluoromethanesulfonic acid, chlorosulfonic acid or fluorosulfonicacid; a phosphonic acid, e.g. orthophosphonic acid, pyrophosphonic acidor benzenephosphonic acid; a carboxylic acid, e.g. chloroacetic acid,dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, oxalicacid or terephthalic acid; or a perhalic acid such as perchloric acid.The protonic acid may also be an acidic ion exchange resin.

The catalyst system used in the process according to the invention maybe homogeneous or heterogeneous. Preferably, it is homogeneous.

The ratio of the number of moles of phosphine per gram atom of GroupVIII metal is not critical. Preferably, it is in the range of from 1 to1000, more preferably from 2 to 500, especially from 10 to 100.

The ratio of the number of moles of phosphine per mole of protonic acidis not critical. The function of the protonic acid is to provide asource of protons. Accordingly, the protonic acid may be generated insitu. Preferably,. it is in the range of from 0.1 to 50, more preferablyfrom 0.5 to 5.

Examples of tertiary amines include optionally substituted aromatic,heterocyclic tertiary amines such as pyridines, quinolines,isoquinolines, pyrimidines, pyrazines, triazoles, triazines,pyridazines, purines, thiazoles, benzimidazoles, oxazoles, pyrazoles andisothiazoles; aliphatic tertiary amines such as dialkylamines e.g.dimethylamine or diethylamine; and optionally substituted tertiaryanilines such as, N,N-dialkylanilines, e.g. N,N-dimethylaniline.

Preferably, the tertiary amine is a pyridine or an N,N-dialkylaniline.

Preferred examples of pyridines are pyridine alkyl-substituted pyridinessuch as 2,6-dimethylpyridine and polyvinylpyridine.

The number of equivalent of tertiary amine present per mole of protonsis preferably at least 0.5, more preferably, at least 1, even morepreferably, at least 2, especially at least 5. Depending upon theparticular carbonylation process in which the catalyst system is to beused, the tertiary amine is preferably present in catalytic quantitiesor in solvent quantities.

When the tertiary amine is present in catalytic quantities, the numberof equivalent of tertiary amine per mole of protons is preferably in therange of from 0.1 to 200, more preferably, 0.5 to 100, especially 1 to50.

When the tertiary amine is present in solvent quantities, the number ofequivalents of tertiary amine per mole of protons is preferably in therange of from 1 to 2,500, more preferably 1.5 to 1500, especially 10 to1000.

For the avoidance of doubt, the tertiary amine may not be a phosphine,for example the phosphine having an aromatic substituent containing animino nitrogen atom.

As has been stated above, it has been found that compositions accordingto the invention have good activity in the carbonylation of unsaturatedhydrocarbons.

Accordingly, the invention further provides the use of a catalyst systemas defined hereinbefore in the carbonylation of an acetylenically orolefinically unsaturated hydrocarbon.

According to another aspect, the invention provides a process for thecarbonylation of an acetylenically or olefinically unsaturated compound,which comprises reacting an acetylenically or olefinically unsaturatedcompound with carbon monoxide in the presence of a catalyst system asdefined above.

The acetylenically or olefinically unsaturated compound is preferably anasymmetric acetylene or olefin, most preferably an alpha acetylene orolefin.

An olefinically unsaturated compound is preferably a substituted orunsubstituted alkene or cycloalkene having from 2 to 30, preferably from3 to 20 carbon atoms per molecule.

An acetylenically unsaturated compound is preferably a substituted orunsubstituted alkyne having from 2 to 20, especially from 3 to 10 carbonatoms per molecule.

The acetylenically or olefinically unsaturated compound may contain oneor more acetylenic or olefinic bonds, for example one, two or threeacetylenic or olefinic bonds.

An olefin or acetylene may be substituted by, for example, a halogenatom, a cyano group, an acyl group such as acetyl, an acyloxy group suchas acetoxy, an amino group such as dialkylamino, an alkoxy group such asmethoxy, a haloalkyl group such as trifluoromethyl, a haloalkoxy groupsuch as trifluoromethoxy, an amido group such as acetamido, or a hydroxygroup. Some of these groups may take part in the reaction, dependingupon the precise reaction conditions. For example, lactones may beobtained by carbonylating certain acetylenically unsaturated alcohols,for example 3-butyn-1-ol, 4-pentyn-1-ol or 3-pentyn-1-ol. Thus3-butyn-1-ol may be converted into α-methylene-γ-butyrolactone.

Examples of alkynes are: ethyne, propyne, phenylacetylene, 1-butyne,2-butyne, 1-pentyne, 1-hexyne, 1-heptyne. 1-octyne, 2-octyne, 4-octyne,1.7-octadiyne, 5-methyl-3-heptyne, 4-propyl-2-pentyne, 1-nonyne,benzylethyne and cyclohexylethyne.

Examples of alkenes are: ethene, propene, phenylethene, 1-butene,2-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 2-octene, 4-octene.cyclohexene and norbornadiene.

The acetylenically or olefinically unsaturated compound can be both anacetylene and an olefin, for example as in 3-methyl-but-3-ene-2-yne.

It has been found that catalyst systems according to the invention arehighly selective for acetylenic groups in the presence of olefinicgroups.

The unsaturated compound may be carbonylated alone or in the presence ofother reactants, for example, hydrogen or a nucleophilic compound havinga removable hydrogen atom. An example of a nucleophilic compound havinga removable hydrogen atom is a hydroxyl-containing compound.

A hydroxyl-containing compound is preferably an alcohol, water, acarboxylic acid or a silanol.

The ability of the catalyst systems according to the invention tocarbonylate silanols is particularly surprising.

Any alcohol used may be aliphatic, cycloaliphatic or aromatic and maycarry one or more substituents. The alcohol preferably comprises up to20 carbon atoms per molecule. It may be, for example, an alkanol, acycleoalkanol or a phenol. One or more hydroxyl groups may be present,in which case several products may be formed, depending on the molarratio of the reactants used.

Examples of alkanols include methanol, ethanol, 1-propanol, 2-propanol,1-butanol, 2-butanol, 2-methylpropan-1-ol, and 2-methylpropan-2-ol.

Examples of phenols include phenol, alkylphenols, catechols, and2,2-bis(4-hydroxyphenyl)propane.

Other examples of alcohols include polyvalent alcohols, in particularlower sugars such as glucose, fructose, mannose, galactose, sucrose,aldoxose, aldopentose, altrose, allose, talose, gulose, idose, ribose,arabonose, xylose, lyxose, erythrose or threose, cellulose, benzylalcohol, 2,2-bis(hydroxymethyl)-1-butanol, stearyl alcohol,cyclohexanol, ethylene glycol, 1,2-propanediol, 1,4-butanediol,polyethyleneglycol, glycerol and 1,6-hexanediol.

An interesting reaction has been found to take place when an olefin iscarbonylated with an alkanol and formaldehyde in the presence of thecatalyst system according to the invention. Without wishing to be boundby any theory it is believed that the alcohol and formaldehyde reacttogether to generate a hemiacetal. The hemiacetal, which is ahydroxyl-containing compound, then reacts with the olefin to afford analkyloxymethyl alkanoate. For example, ethene, carbon monoxide,formaldehyde and methanol may be reacted together to affordmethoxymethyl propionate.

The process according to the present invention can be carried out usinga wide variety of carboxylic acids. For example, the carboxylic acidsmay be aliphatic, cycloaliphatic or aromatic and may carry one or moresubstituents, such as those named in connection with the acetylenicallyand olefinically unsaturated compounds.

Carboxylic acids preferably used in the process according to theinvention include those containing up to 20 carbon atoms. One or morecarboxylic acid groups may be present, thus allowing various products asdesired, depending on the molar ratio of the reactants used. Thecarboxylic acids may, for example, be alkanecarboxylic acids oralkenecarboxylic acids. Examples of carboxylic acids are: formic acid,acetic acid, propionic acid, n-butyric acid, isobutyric acid, pivalicacid, n-valeric acid, n-caproic acid, caprylic acid, capric acid, lauricacid, myristic acid, palmitic acid, stearic acid, benzoic acid,o-phthalic acid, m-phthalic acid, terephthalic acid and toluic acid.Examples of alkenecarboxylic acids are acrylic acid, propiolic acid,methacrylic acid, crotonic acid, isocrotonic acid, oleic acid, maleicacid, fumaric acid, citraconic acid and mesaconic acid.

A silanol is preferably a trialkylsilanol, more preferably atri(C₁₋₆)alkylsilanol such as triethylsilanol.

It will be appreciated that the unsaturated hydrocarbon and thehydroxyl-containing compound may be the same compound.

When an acetylenically unsaturated compound is reacted with water andcarbon monoxide, an alpha,beta-unsaturated carboxylic acid is formed. Ifan alcohol is used instead of water, an alpha,beta-unsaturatedcarboxylic ester is formed. If a carboxylic acid is used instead ofwater, an alpha,beta-unsaturated anhydride is formed. Thealpha,beta-unsaturated product may undergo further reaction dependingupon the reaction conditions employed.

When an olefinically unsaturated compound is reacted with carbonmonoxide and water, a carboxylic acid is formed. If an alcohol is usedinstead of water, a carboxylic ester is formed: for example reaction ofethene, carbon monoxide and water affords methyl propionate, if acarboxylic acid is used instead of water, an anhydride is formed: forexample reaction of ethene, carbon monoxide and propionic acid affordspropionic anhydride. If a silanol is used instead of water, a silylester is obtained: for example reaction of ethene, carbon monoxide andtriethylsilanol affords triethylsilyl propionate.

A surprising property of catalyst systems according to the invention istheir ability to selectively carbonylate unsaturated compounds with acidsensitive hydroxy compounds such as tertiary alkanols, for example2-methyl-propan-2-ol (tertiary butanol) and silanols, for example.triethylsilanol.

According to a preferred aspect therefore, the invention provides aprocess for the carbonylation of an acetylenically or olefinicallyunsaturated compound, in which an acetylenically or olefinicallyunsaturated compound is reacted with carbon monoxide and a tertiaryalkanol or a silanol in the presence of a catalyst system as definedpreviously.

The catalyst system according to the invention has also been found to besurprisingly good for the carbonylation of acetylenically unsaturatedcompound in the presence of allenes. According to a preferred aspect,therefore, the present invention provides a process for thecarbonylation of an acetylenically unsaturated compound, in which anacetylenically unsaturated compound is reacted with carbon monoxide inthe presence of an allene and a catalyst system as defined above.

Preferably the allene is present in an amount of from 0.3 to 10 per centby weight, based upon the weight of the acetylenically unsaturatedcompound.

When an allene is present, the tertiary amine is preferably used incatalytic amounts.

It is not essential to use a separate solvent in the process accordingto the invention. In some cases, however, it may be desirable to use aseparate solvent. Any inert solvent can be used for that purpose. Saidsolvent may, for example, comprise sulfoxides and sulfones, for exampledimethylsulfoxide, diisopropylsulfone or tetrahydrothiophene-2,2-dioxide(also referred to as sulfolane), 2-methylsulfolane, 3-methylsulfolane,2-methyl-4-butylsulfolane; aromatic hydrocarbons such as benzene,toluene, xylenes; esters such as methylacetate and butyrolactone;ketones such as acetone or methyl isobutyl ketone, ethers such asanisole, 2,5,8-trioxanonane (also referred to as diglyme), diphenylether and diisopropyl ether, and amides such as N,N-dimethylacetamide orN-methylpyrrolidone.

The process according to the present invention is conveniently effectedat a temperature in the range of from 10° C. to 200° C., in particularfrom 20° C. to 130° C.

The process according to the invention is preferably effected at apressure of from 1 to 100 bar. Pressures higher than 100 bar may beused, but are generally economically unattractive on account of specialapparatus requirements.

The molar ratio of the hydroxyl-containing compound to the unsaturatedhydrocarbon may vary between wide limits and generally lies within therange of 0.01:1 to 100:1.

The carbon monoxide required for the process according to the presentinvention may be used in a practically pure form or diluted with aninert gas, for example nitrogen. The presence of more than smallquantities of hydrogen in the gas stream is undesirable on account ofthe hydrogenation of the unsaturated hydrocarbon which may occur underthe reaction conditions. In general, it is preferred that the quantityof hydrogen in the gas stream supplied is less than 5 vol %.

The catalyst systems used in the process according to the invention areconstituted in a liquid phase. They may be prepared by any convenientmethod. Thus they may be prepared by combining a separate Group VIIImetal compound, the phosphine (I). the protonic acid and the tertiaryamine in a liquid phase. Alternatively, they may be prepared bycombining a Group VIII metal compound and an acid addition salt of thephosphine and the tertiary amine in a liquid phase. Alternatively, theymay be prepared from a Group VIII metal compound which is a complex of aGroup VIII metal with the phosphine, the protonic acid and the tertiaryamine in a liquid phase. Alternatively, they may be prepared bycombining a Group VIII metal compound, the phosphine and an acidaddition salt of the tertiary amine in a liquid phase.

The liquid phase may conveniently be formed by one or more of thereactants with which the catalyst system is to be used. Alternatively,it may be found by a solvent. It may also be found by one of thecomponents of the catalyst system, for example a tertiary amine.

Phosphines having an aromatic substituent which contains an iminonitrogen atom are known in the art. They are conveniently prepared byreacting a phosphorus halide or alkali metal phosphide with aappropriate alkali metal or halide derivative of an aromatic compoundcontaining an imino nitrogen atom.

The invention will now be further described by the following exampleswhich are illustrative and which are not intended to be construed aslimiting the scope of the invention.

PREPARATION 1 Preparation of diphenyl-(6-methyl-2-pyridyl)-phosphine

All manipulations were carried out in an inert atmosphere (nitrogen orargon). Solvents were dried and distilled prior to use. 36 ml of a 1.6Mn-butyllithium solution in hexane was added to 40 ml diethyl ether, andthe mixture was cooled to -40° C. To the stirred mixture was added inthe course of 20 minutes a solution of 10 g 2-bromo-6-methylpyridine in15 ml diethyl ether; during this addition, the temperature was kept at-40° C. After the addition, the temperature was raised to -5° C., keptthere for 5 minutes, and then lowered again to -40° C. A solution of12.8 g chlorodiphenylphosphine in 15 ml diethyl ether was added in thecourse of 15 minutes to the stirred mixture. After the addition, themixture was warmed to room temperature, the solvents were removed invacuo, and 50 ml water and 50 ml dichloromethane were added. After 5minutes of vigorous stirring, the dichloromethane layer was separated.The water layer was extracted with two 50 ml portions ofdichloromethane, the organic reactions were combined, and the solventremoved in vacuo. The residue was crystallized from toluene/hexane toafford 12 g (75%) of diphenyl-(6-methyl-2-pyridyl)-phosphine asoff-white crystals. The product was characterized by ³¹ P NMR:δ_(p)=-5.6 ppm.

PREPARATION 2 Preparation of diphenyl-(3-methyl-2-pyridyl)-phosphine

This compound was prepared as described in Preparation 1, but using 10.0g of 2-bromo-3-methylpyridine instead of the 2-bromo-6-methylpyridine.It was characterized by ³¹ P NMR:δ_(p) =-8.1 ppm.

PREPARATION 3 Preparation of phenyl-bis(6-methyl-2-pyridyl)-phosphine

This compound was prepared as described in Preparation 1, but using 5.2g of phenyldichlorophosphine instead of the chlorodiphenylphosphine. Itwas characterized by ³¹ P NMR:δ_(p) =-5.1 ppm.

PREPARATION 4 Preparation of tris(6-methyl-2-pyridyl)-phosphine

This compound was prepared as described in Preparation 1, but using 2.7g of phosphorus trichloride instead of the chlorodiphenylphosphine. Itwas characterized by ³¹ P NMR:δ_(p) =-3.8 ppm.

PREPARATION 5 Preparation of diphenyl-(4,6-dimethyl-2-pyridyl)-phosphine

This compound was prepared as described in Preparation 1. but using 10.8g of 2-bromo-4,6-dimethylpyridine instead of the2-bromo-6-methylpyridine. It was characterized by ³¹ P NMR:δ_(p) =-5.6ppm.

PREPARATION 6 Preparation of diphenyl-(6-methoxy-2-pyridyl)-phosphine

2.7 g Sodium was added to 100 ml liquid ammonia at -80° C., and then15.2 g of triphenylphosphine was added in 6 portions with stirring. Thesolution was slowly warmed to -40° C., kept at that temperature for 30min. and then cooled again to -80° C. Then, 3.1 g of ammonium chloridewas added to the stirred solution, followed by 10.9 g of2-bromo-6-methoxypyridine in three portions. The cooling bath wasremoved and the ammonia was allowed to evaporate. The residue was workedup with water/dichloromethane as described in Preparation 1.Crystallization from hexane afforded 7 g of a somewhat impure product(characterized by ³¹ P NMR:δ_(p) =-4.4 ppm) which was used as such inthe following Examples.

PREPARATION 7 Preparation of di(n-butyl)-2-pyridyl phosphine

To a magnetically stirred solution of 2.5 g phenyl(2-pyridyl)₂ P in 20mol tetrahydrofuran, cooled to -80° C., was added in the course of 10min 5.9 ml of a 1.6M solution of n-butylLi in hexane. The resultingdeep-red solution was allowed to warm to room temperature, and analysisof the solution by ³¹ P NMR showed it to contain the phosphide(n-butyl)(2-pyridyl)PLi as the only phosphorus-containing compound(β_(p) =-16.3 ppm).

The solution was cooled to -40° C. and a solution of 1.3 g 1-bromobutanein 10 ml tetrahydrofuran was added. The mixture was again warmed to roomtemperature, the solvents were removed in vacuo, and 25 ml ofdiethylether and 10 ml of water were added. After 10 minutes ofstirring, the organic layer was separated and the water layer wasextracted with 10 ml of ether. The organic layers were combined and thesolvent was removed in vacuo (66 Pa). The resulting light-yellow liquidwas analyzed by ¹ H, ¹³ C and ³¹ P NMR and shown to consist of a 1:1(molar ratio) mixture of 2-phenylpyridine and (n-butyl)₂ (2-pyridyl)P(δ_(p) =-19.5 ppm).

PREPARATION 8 Preparation of dimethyl 2-pyridyl phosphine andmethylphenyl-2-pyridyl phosphine

The method of Preparation 7 was repeated, except that a 1.6M solution ofmethylLi in diethylether was used instead of the n-butylLi solution, and1.3 g of iodomethane instead of the bromobutane. The reaction productwas a mixture of (methyl)₂ 2-pyridyl)P, methyl phenyl 2-pyridylP and2-phenyl pyridine in the approximate ratio 70:30:60, from which the(methyl)₂ (2-pyridyl)P was isolated by distillation.

The physical characteristics of the products were δ_(p) =-41.2 ppm(dimethyl-2-pyridylphosphine) and δ_(p) =-24.1 ppm(methylphenyl-2-pyridylphosphine).

PREPARATION 9 Preparation of n-butyl tert-butyl 2-pyridyl phosphine

The method of Preparation 7 was repeated, except that 5.6 ml of a 1.7Msolution of t-butylLi in pentane was used instead of the n-butylLisolution. The final product was identified as n-butyl t-butyl 2-pyridylPby NMR analysis (δp.sub. =-7.4 ppm).

PREPARATION 10 Preparation of dimethyl 2-pyridylphosphine

The method of Preparation 8 was repeated, except that 1.91 gmethyl(2-pyridyl)₂ P and only 0.7 g iodomethane were used. Workup asdescribed in Example 1 afforded dimethyl 2-pyridyl phosphine, which wasfurther purified by distillation (65% yield). (δ_(p) =-41.2 ppm).

PREPARATION 11

Preparation of n-butyl(4-methoxyphenyl)(2-pyridyl)phosphine

All manipulations were carried out in an inert atmosphere (nitrogen orargon). Solvents were dried and distilled prior to use. 18 ml of a 1.6Mn-butyllithium solution in hexane was added to 30 ml diethyl ether, andthe mixture was cooled to -40° C. To the stirred mixture was added inthe course of 20 minutes a solution of 4.6 g 2-bromopyridine in 15 mldiethyl ether, during this addition, the temperature was kept at -40° C.After the addition, the temperature was raised to -5° C., kept there for5 minutes, and then lowered again to -40 ° C. The resulting solution wasadded to a cooled (-40° C.) solution of 7.6 g4-methoxyphenyl-bis(2-pyridyl)phosphine in 30 ml THF. The mixture waswarmed to room temperature. After stirring for 10 minutes, the solventswere removed in vacuo. Water (25 ml) and dichloromethane (25 ml) wereadded. After 5 minutes of vigorous stirring, the dichloromethane layerwas separated. The water layer was extracted with two 25-ml portions ofdichloromethane, the organic fractions were combined, and the solventremoved in vacuo. The residue was distilled, giving 4.7 g (60%) of(n-butyl) (4-methoxyphenyl) (2-pyridyl) phosphine as a yellowish liquid.The product was characterized by ³¹ P NMR:δ_(p) =-14.9 ppm.

In this experiment, n-butyllithium is believed to react with2-bromopyridine to afford a mixture of n-butylbromide and2-pyridyllithium. Then the 2-pyridyllithium reacts with4-methoxy-bis(2-pyridyl)phosphine to afford4-methoxyphenyl(2-pyridyl)lithium phosphide (and 2,2'-bipyridine). Thelithium phosphide then reacts with n-butylbromide to afford (n-butyl)(4-methoxyphenyl)(2-pyridyl)phosphine.

PREPARATION 12 Preparation of methyl di(2-pyridyl)phosphine

All manipulations were carried out in an inert atmosphere (nitrogen orargon). Solvents were dried and distilled prior to use. 36 ml of a 1.6Mn-butyllithium solution in hexane was added to 40 ml diethyl ether, andthe mixture was cooled to -40° C. To the stirred mixture was added inthe course of 20 minutes a solution of 9.2 g 2-bromopyridine in 15 mldiethyl ether; during this addition, the temperature was kept at -40° C.After the addition, the temperature was raised to -5° C., kept there for5 minutes, and then lowered again to -40° C. A solution of 3.4 gmethyldichlorophosphine in 15 ml diethyl ether was added to the stirredmixture. After the addition, the mixture was warmed to room temperature,the solvents were removed in vacuo, and 50 ml water and 50 mldichloromethane were added. After 5 minutes of vigorous stirring, thedichloromethane layer was separated. The water layer was extracted withtwo 50-ml portions of dichloromethane, the organic fractions werecombined, and the solvent removed in vacuo. The residue was distilled,giving 4.0 g (68%) of methyl-bis(2-pyridyl)phosphine as a yellowishliquid. The product was characterized by ³¹ P NMR:δ_(p) =-20.5 ppm.

EXAMPLE 1

A 250 ml stainless steel magnetically stirred autoclave was filled with0.1 mmol palladium(II)acetate, 5 mmol bisphenyl(2-pyridyl)phosphine, 4mmol paratoluenesulfonic acid, 50 ml (620 mmol) pyridine and 10 ml (65mmol) triethylsilanol. Air was then evacuated from the autoclave, andthen carbon monoxide (30 bar) and ethylene (20 bar) were added. Theautoclave was then sealed and heated to a temperature of 110° C. After areaction time of 4.5 hours, a sample of the contents of the autoclavewas withdrawn and analyzed by gas liquid chromatography.

Triethylsilylpropionate was formed with a selectivity of 60% (based onsilanol). Di-triethylsilyl ether was also formed, with a selectivity ofabout 40% (based on silanol). The mean conversion rate was calculated to200 mol ethene/gram atom Pd/hour.

COMPARATIVE EXAMPLE A

The method of Example 1 was repeated, but using triphenylphosphineinstead of bisphenyl(2-pyridyl)phosphine, and withdrawing a sample ofthe contents of the autoclave after 5 hours instead of 4.5 hours. Onlytraces of triethylsilyl propionate were detected.

COMPARATIVE EXAMPLE B

The method of Comparative Example A was repeated, but using 50 mlmethylpropionate instead of 50 ml pyridine and heating to 80° C. insteadof 110° C. Di(triethylsilyl)ether was formed with a selectivity of >90%.Only traces of triethylsilylpropionate were detected.

EXAMPLE 2

A 250 ml stainless steel, magnetically stirred autoclave was filled with0.1 mmol palladium(II)acetate, 5 mmol bisphenyl(2-pyridyl)phosphine, 4mmol p-toluenesulfonic acid, 40 ml (500 mmol) pyridine, 20 ml methanoland 5 g paraformaldehyde. Air was then evacuated from the autoclave, andthen carbon monoxide (30 bar) and ethene (20 bar) were added. Theautoclave was then sealed and heated to a temperature of 110° C. After areaction time of 5 hours, a sample of the contents of the autoclave waswithdrawn and analyzed by gas liquid chromatography. Two products werefound; methoxymethylpropionate, which had been formed with a selectivityof 10%, and methylpropionate, which had been formed with a selectivityof 90%. The mean reaction rate was calculated to be 200 mol ethene/gramatom Pd/hour.

COMPARATIVE EXAMPLE C

The method of Example 2 was repeated, but using triphenylphosphineinstead of bisphenyl(2-pyridyl)phosphine. Only traces of carbonylatedproducts were observed.

COMPARATIVE EXAMPLE D

The method of Example 2 was repeated, but using no pyridine, and 50 mlmethanol instead of 20 ml methanol. The sample of the contents of theautoclave was withdrawn after a reaction time of 2 hours. Only traces ofmethoxymethylpropionate were observed. Methylpropionate was found tohave been formed with a selectivity of >95%. The mean reaction rate wascalculated to be 1000 mol ethene/gram atom Pd/hour.

EXAMPLE 3

The method of Example 2 was repeated but using 40 ml (350 mmol)2,6-dimethylpyridine instead of 40 ml pyridine, heating to 125° C.instead of 110° C., and analyzing a sample of the contents of theautoclave after 4.5 hours instead of 5 hours. Methoxymethylpropionatewas found to have been formed with a selectivity of 35%. andmethylpropionate with a selectivity of 60%. The mean reaction rate wascalculated to be 150 mol ethene/gram atom Pd/hour.

EXAMPLE 4

The method of Example 2 was repeated, but using 40 ml (350 mmol)2,6-dimethylpyridine instead of pyridine, 10 ml methanol instead of 20ml methanol and heating to 125° C. instead of 110° C.Methoxymethylpropionate was found to have been formed with a selectivityof 60%, and methyl propionate with a selectivity of 30%. The meanreaction rate was calculated to be 100 mol ethene/gram atom Pd/hour.

EXAMPLE 5

A 250 ml stainless steel magnetically stirred autoclave was filled with0.1 mmol palladium(II)acetate, 2 mmol bisphenyl(2-pyridyl)phosphine, 10mmol paratoluenesulfonic acid, 40 ml (500 mmol) pyridine and 20 mlmethanol. Air was then evacuated from the autoclave and then 20 barethene and 30 bar carbon monoxide were added. The autoclave was thensealed and heated to 110° C. After a reaction time of 5 hours, a sampleof the contents of the autoclave was withdrawn and analyzed by gasliquid chromatography. Methylpropionate was found to have been formed.The mean reaction rate was calculated to be 300 mol ethene/gram atomPd/hour. No methyltriphenylphosphonium tosylate was detected, indicatingthat the catalyst had remained stable during the course of the reaction.

COMPARATIVE EXAMPLE E

The method of Example 5 was repeated but using triphenylphosphineinstead of bisphenyl(2-pyridyl)phosphine. Methyl propionate wasdetected, but the mean reaction rate was calculated to be less than 10mol ethene/gram atom Pd/hour.

COMPARATIVE EXAMPLE F

The method of Example 5 was repeated, but usingtris(p-chlorophenyl)phosphine instead of bisphenyl(2-pyridyl)phosphine,4 mmol paratoluenesulfonic acid, heating to 130° C., and withdrawing asample from the autoclave after 4 hours. Methyl propionate was detected.The mean reaction rate was calculated to be less than 10 mol ethene/gramatom Pd/hour.

EXAMPLE 6

The method of Example 5 was repeated, but using 40 ml (320 mmol)N,N-dimethylaniline instead of 40 ml pyridine heating to 100° C. insteadof 110° C., and withdrawing a sample from the autoclave after 11/2 hourinstead of 5 hours. Methyl propionate had been formed. The mean reactionrate was calculated to be 700 mol ethene/gram atom Pd/hour.

EXAMPLE 7

The method of Example 5 was repeated, but using 20 ml (270 mmol)propionic acid instead of 20 ml methanol, and heating to 90° C. insteadof 110° C. Propionic anhydride was formed. The mean reaction rate wascalculated to be 250 mol ethene/gram atom Pd/hour.

EXAMPLE 8

The method of Example 5 was repeated, but using 5 mmolbisphenyl(2-pyridyl)phosphine, 4 mmol paratoluenesulfonic acid, 30 mlmethanol, and heating for 3 hours instead of 5 hours. Methyl propionatewas formed. The mean conversion rate was calculated to be 800 molethene/gram atom Pd/hour.

EXAMPLE 9

The method of Example 5 was repeated, but using 5 mmolbisphenyl(2-pyridyl)phosphine, 4 mmol trifluoromethanesulfonic acid, andwithdrawing a sample of the contents of the autoclave after 3 hours.Methyl propionate was formed. The mean reaction rate was calculated tobe 1000 mol ethene/gram atom Pd/hour.

EXAMPLE 10

The method of Example 5 was repeated, but using 5 mmolbisphenyl(2-pyridyl)phosphine, 4 mmol paratoluenesulfonic acid, 50 mlmethanol instead of 20 ml, and 10 g (95 mmol) poly-4-vinylpyridine(cross-linked) instead of 40 ml pyridine. Methyl propionate was formed.The mean reaction rate was calculated to be 400 mol ethene/gram atomPd/hour.

EXAMPLE 11

A 300 ml magnetically-stirred stainless steel autoclave was successivelyfilled with 0.025 mmol palladium(II)acetate, 1 mmol bisphenyl(6-methyl-2-pyridyl) phosphine, 2 mmol 2-methyl-2-propylsulfonic acid,30 ml methyl methacrylate as solvent, 30 ml methanol and 10 mmoldimethylaniline. Air was then evacuated from the autoclave, and then 30ml propyne containing 0.4% allene was added. Carbon monoxide was thenadded to a pressure of 60 bar. The autoclave was then sealed and heatedto a temperature of 60° C. After a reaction time of 0.1 hour at 60° C.,a sample of the contents of the autoclave was analyzed by gas liquidchromatography. From the results of the analysis, the selectivity tomethyl methacrylate was calculated to be 99.94% and the mean conversionrate was calculated to be 90,000 mol propyne/gram atom Pd/hour.

EXAMPLE 12 TO 18 AND COMPARATIVE EXAMPLE G

The method of

EXAMPLE 11 was repeated using different tertiary amines, and differentamounts of allene in the propyne. The results are summarized in Table 1.

The results demonstrate that the inhibitory effect of allene on thecatalyst can be counteracted by using tertiary amines.

                                      TABLE 1                                     __________________________________________________________________________    Carbonylation of Propyne and Methanol to give methyl methacrylate             Ex-                                             Selec-                                                                             Mean Conversion          am-                                     %   Temp                                                                              tivity                                                                             rate (mol propyne/       ple                                                                              Ligand (mmol)                                                                           Acid (mmol)                                                                           Solvent                                                                            Promoter (mmol)                                                                             allene                                                                            (°C.)                                                                      (%)  gat.Pd/hr)               __________________________________________________________________________    11                                                                                ##STR5## CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR6##     0.4 60  99.94                                                                              90,000                   12                                                                                ##STR7## CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR8##     0.4 60  99.0 67,000                   13                                                                                ##STR9##  CH.sub.3 SO.sub.3 H (2)                                                              MMA                                                                                 ##STR10##    0.4 60  99.94                                                                              18,000                   14                                                                                ##STR11##                                                                              CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR12##    0.4 60  99.9 30,000                   15                                                                                ##STR13##                                                                              CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR14##    0.4 60  99.9  9,000                   16                                                                                ##STR15##                                                                              CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR16##    0.4 60  99.9 15,000                   17                                                                                ##STR17##                                                                              CH.sub.3 SO.sub.3 H (2)                                                               MMA                                                                                 ##STR18##    2.0 60  99.9  7,000                   18                                                                                ##STR19##                                                                              (CH.sub.3).sub.3 CSO.sub.3 H (2)                                                      MMA                                                                                 ##STR20##    7.0 45  99.9  6,000                       ##STR21##                                                                              CH.sub.3 SO.sub.3 H (2)                                                               MMA  None          0.4 60  98.9  7,000                   __________________________________________________________________________     Key                                                                           MMA Methylmethacrylate                                                        φ Phenyl group                                                       

What is claimed is:
 1. A catalyst system which comprises:a) a Group VIIImetal compound; b) a phosphine having an aromatic substituent whichcontains an imino nitrogen atom; c) a protonic acid; and d) a tertiaryamine selected from the group consisting of a pyridine and anN,N-dialkylaniline.
 2. The catalyst system of claim 1 wherein the GroupVIII metal compound is a palladium compound.
 3. The catalyst system ofclaim 2 wherein an imino group in an aromatic substituent containing animino nitrogen atom is linked to a phosphorus atom through a singlebridging carbon atom.
 4. The catalyst system of claim 3 wherein thephosphine is selected from the group consisting of 2-pyridyl,2-pyrimidyl and 2-triazinylphosphine.
 5. The catalyst system of claim 1wherein the number of equivalents of tertiary amine per mole of protonicacid is at least
 1. 6. The catalyst system of claim 5 wherein the numberof equivalents of tertiary amine per mole of protonic acid is in therange of from 1.5 to 1,500.